Conventionally, water-preventing sealants comprising organic materials of asphalt-series, rubber-series, and resin-series, are employed for the water leakage prevention and sealing at sections where sealing is required, for example, concrete joints, a constructed joined part between a section made of concrete and a section made of another material, or a joint part of concrete secondary products, in civil engineering and building constructions, and particularly, for water leakage prevention/sealing of subsurface constructions. Further, as other water-preventing sealants, water-preventing sealants comprising inorganic materials are known, and those that harden, such as cement-series water-preventing sealants, and those of smectite-series are used. As the smectite-series water-preventing sealants, water-preventing sealants employing a bentonite material having the property of swelling by the absorption of water, are known. The water-preventing sealant comprising a bentonite-series material is used in such a manner that, for example, a bentonite in powdery or granular form is either applied as it is, alternatively, a bentonite in powdery or granular form is loaded into a container of corrugated board, nonwoven fabric, woven fabric, or the like; a bentonite in powdery or granular form is interposed between pieces of corrugated board, nonwoven fabric, woven fabric; or a bentonite is solidified with an adhesive or a resin, to form a sealing panel, sealing sheet, or a sealing rope.
In the case of these conventional water-preventing sealants, however, because lack in amount or localization (omnipresence) of the bentonite occurred, or because the conventional water-preventing sealants neither had adhesion property or plasticity, they did not well follow structures having complicated shapes, and they could neither attain improvement in applicability nor retention of the water-preventing effect for a long period of time.
The conventional organic water-preventing sealants, that is, asphalt-series, rubber-series, and resin-series water-preventing sealants, were lowered in water-preventing performance with the passage of time, for example, owing to their deterioration by the environment where they were placed or their decomposition by bacteria in soil. Therefore, in the conventional sealants, there was a problem as a material in view of retention of the level of original water-preventing effect for a long period of time. Further, even in the case of inorganic water-preventing sealants, such as cement-series water-preventing sealants, which require curing after the application, a certain period of time are required until they are dried completely after the application, so that the influence of weather at the time of the application or after the application has to be taken into account. It put various restrictions on the execution of work. Further, none of asphalt-series, rubber-series, resin-series, and cement-series water-preventing sealants had a self-sealing property.
On the other hand, smectite-series water-preventing sealants comprising a powder or granular bentonite do not need curing, they are excellent in water-preventing performance and long-term stability, and they have a self-sealing property by absorbing water to swell and close spaces around the water-preventing sealant.
However, they had a problem that they were poor in working applicability. When the substrate surface where sealing was required was rough or had a complicated shape, such as a step, since conventional bentonite water-preventing sealants could not be brought in close contact with the substrate surface, the substrate surface was required to be made smooth prior to application of the sealants. Further, conventional bentonite water-preventing sealants did not well follow the substrate when applied, and there were spaces remained between bentonite particles in the conventional bentonite water-preventing sealants. Therefore, there existed a clearance (space) between the water-preventing sealant and the substrate, and there also existed clearances (spaces) between bentonite particles, until the bentonite absorbs water, to swell, and thus there was a problem that any water-preventing effect was not available until the water-preventing sealant swells, to close the spaces.
Accordingly in order to solve these problems of the long-term stability, the working applicability, and the water-preventing effect, water-preventing sealants formed in a bole state by kneading a bentonite and a gelled base oil are proposed (U.S. Pat. No. 4,209,568, U.S. Pat. No. 4,279,547, and U.S. Pat. No. 5,704,970). Since these bentonite water-preventing sealants in a bole state have plasticity and therefore can be brought in close contact with the substrate where sealing is required. The sealants in a bole state permit any space between the water-preventing sealant and the substrate, and any spaces between the bentonite particles in the water-preventing sealant, to exist minimally at the time of the application. Therefore, in the sealant in a bole state, a water-preventing effect can be expected immediately after the application, and an excellent water-preventing effect having self-sealing property owing to the swellability of bentonite, can be obtained.
These bentonite-series water-preventing sealants in a bole state have, however, the faults that the production is troublesome and that the cost is high, since a specified gelled base oil is used. Further, although their water-preventing effect is high, these sealants are still unsatisfactory on the following views. That is, the sealants in a bole state absorb water, to swell, for example, during the application, thereby making the application difficult in some cases; and, when the water-preventing sealant comes in contact with running water after they are applied, the impermeable layer of the swollen water-preventing sealant is washed away little by little, thereby lowering the water-preventing effect, in some cases.
U.S. Pat. No. 5,116,413 discloses sealing agents prepared by mixing well a water-swellable polymer, such as bentonite, with a viscous hydrophobic substance whose viscosity is lost upon heating, selected from among a tar-like product, bitumen, and vaseline, and a small amount of a hydrophilic substance, selected from polyhydric alcohols or water. These sealing agents adhere to a wide variety of materials, have ability to swell in water, and have plasticity. However, these sealing agents are each a soft mixture to be used by filling it in a casing or a container; for example, by packing it in a bag. Therefore, if this sealing agent is used as it is without placing it in a container or a casing, shape-retainability is poor, and further, this sealing agent becomes fluidized when heated, particularly at a high temperature.